Crown closures



May 8, 1962 J. H. BRILLINGER CROWN CLOSURES Filed Dec. 9, 1957 Uite rates This invention relates to container closures and to a process of making container closures. More particularly this invention relates to crown closures having a liner composed of a sponge-like plastic with a myriad of cell spaces.

In seeking satisfactory materials for crown liners the industry has been guided by several requirements. Among these are that the material be inertthat is, not add to or distract from the natural flavor and odor properties of the contents of the bottle; that it possess good resiliency and sealing efliciency as well as chemical stability and adaptability to mass production methods. For many years natural or compounded cork has been the most widely used material. This is not to say that cork has been found perfect, or for that matter satisfactory in every one of the above characteristics, but rather that it at least has been found to contain the best combinations of properties and that by various modifications certain drawbacks have been overcome to some extent. For example, cork has not been completely satisfactory from the point of view of lack of interaction of the cork with the contents of the bottle. Often, especially after long storage times, it is found that cork liners become discolored, build up gummy deposits and stick to the bottle lips when the crown is removed from the bottle. These disadvantages have been overcome to some extent by the use of thin discs or spots made of aluminum, other metals or plastic coated paper in the center of the cork liner. This spot method, of course, adds to the difliculties and expense of making crown liners of cork. Another objection to the use of cork is that the cork is a natural product, and it cannot always be obtained with uniform characteristics.

In view of these drawbacks, there have been many attempts to produce cork substitutes. Among the numerous materials tried have been various modifications of corn stalks, peanut hulls, cellulosic materials and glue compositions. More recently a promising material has been found in the form of vinyl resin plastics. These plastics have the advantages of stability, good flavor and odor characteristics, and adaptability to mass production methods.

Liners made of these plastics, however, have not been entirely successful because it has proven diflicult to obtain as good sealing characteristics and pressure retention properties with these liners as is obtained with cork liners. These difliculties are believed to be due to the fact that plastic liners do not possess the property of compressibility, which is found in cork. The compressibility of cork is generally attributed to the numerous pores or cell-like spaces which exist in the material.

I have discovered how to impart a cellular structure to a vinyl resin liner so as to produce a closure which in addition to the above advantages also has excellent sealing and gas retention properties. Furthermore, these properties are achieved with the employment of very small quantities of liner materials, i.e., less than 0.40 gms. The liner contains a myriad of gas spaces which are substantially uniform in size for the most part and are predominantly non-communicating. In addition, the liner is found to possess a film-like, substantially impervious surface.

This is a highly unique result since former attempts to prepare sponge-like liners have resulted in liners with very irregular cell size, perforations through the surface,

atent ice or so little void volume as to require a very thick liner in order to get significant compressibility. Liners with very irregular cell structure or cells spaces which extend through the surface do not give good seals because the gases and liquids in the container may Work their Way through and around the liner by way of the openings at the surface or by reason of the fact that the irregularly size spaced result in uneven contact of the liner against the bottle neck.

In the drawing the crown cap produced by my invention is shown in perspective section, and is indicated by 1. The liner is 2, with the substantially impervious film at the surface indicated by reference numeral 3. The cellular spaces throughout the liner are indicated at 4- 4.

My crown liner is prepared from a blown and fused plastisol composition. The plastisol composition is made up of a vinyl resin, a plasticizer and a blowing agent, with or without fillers and others additives. The composition is flowed onto the inner surface of a metal crown and fluxed by heating. During fluxing a viscous gel is formed and the blowing agent decomposes to produce hundreds of tiny gas cells in the liner. The blowing agent is chosen so as to decompose after the start of fluxing'. After cooling, the liner is a puffed, rubbery, resilient material. When the crown is placed on a glass container, the liner closely compreses to the configuration of the glass rim and leaves no spaces for leakage.

In addition to the excellent properties of the lined crown produced, my process has great advantages over previous processes for producing cellular liners, which have either placed preformed cellular material in a plastic composition or beaten the composition into a foam before applying it to the crown, since such previous compositions have been diflicult or impossible to send through high speed lining nozzles.

It is well known that plastisols are dispersions of vinyl resin in a non-volatile plasticizer which have the consistency of a paste. When such a mixture is heated to about 93-l07 C. the paste becomes gel-like and losses its fluidity. As temperatures increase to 177 C. or

higher the gel becomes more viscous and greater in strength. The change in properties of the material is brought about by solution of the resin in the plasticizer as the temperature is increased. Upon cooling the composition becomes a tough, rubbery mass.

The plastisol may be made from numerous comercially available thermoplastic materials such as polyvinyl chloride, copolymers of vinylchloride, polyvinyl acetate, copolymers of vinyl acetate, polyvinyl butyrate, polyvinyl alcohols. polyvinylidene chloride, copolymers of vinylidene chloride and polyvinyl aromatic compounds such as polystyrene. The preferred polymer is polyvinyl chloride.

The blowing agents in my process are chosen so that their decomposition temperature is slightly below the final fluxing temperature of the plastisol composition. A difference between maximum fluxing temperatures and decomposition of the blowing agent of about 15 to 30 C. is satisfactory. By so choosing the blowing agent, it is possible to produce blowing when the plastisol is in a fairly tough gel state; i.e., when it is not so fluid that blowing will cause perforations in the surface of the mass nor so well gelled as to prevent proper expansion of gas. There are numerous blowing agents which are suitable, the choice varying with the particular plastisol composition used. Among those which may be used are sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, diazoamino benzene, dinitrosopentamethvlenetetramine, urea-biuret, bisazo formamide. p.o'-oxvbisbenzene sulfonyl hydrazide and azo isobutyronitrile. I have found the nitrogen evolving compounds to be particularly suitable. Though the quantity of blowing agent may be widely varied from 0.1 to 5.0% depending upon the composition and degree of blowing desired, the best results have been realized using less than 1.5% based on the weight of plastisol mixture.

The plasticizer employed may be any of the Well known non-volatile plasticizers for vinyl resins which are known to dissolve the resin at higher temperatures. These include di-2-ethyl hexyl phthalate, di-isooctyl phthalate, acetyl tributyl citrate, di-octyl sebacate, di-hexyl adipate and 2-ethyl hexyl di-phenyl phosphate. The quantity of plasticizer used should be sufficient to form a plastisol of paste-like consistency. Ordinarily the percentage of plasticizer based on the weight of vinyl resin is 60 to 120%, with the preferred amount being from 6595%.

In addition to the plasticizer, resin and blowing agent, various other modifiers are usually desirable, such as lubricants, for example, parafiin wax; wetting agents such as lecithin, propylene glycol laurate, propylene, glycol stearate, zinc resinate, and glycerol mono-oleate; fillers such as talc, wood flour, diatomaceous earth and asbestos; pigments such as carbon black, titanium dioxide, iron oxides and aluminum powder; and stabilizers such as calcium stearate, zinc stearate, organo-tin complexes, epoxy resins and epoxidized oils.

As a specific example, a plastisol composition containing the following ingredients was prepared:

ingredients: Parts by weight No. of grams Vinyl chloride resin powder 100 Talc 30 Acetyl tributyl citrate 70 Calcium stearate 2 Glycerol mono-oleate 2 Dinitrosopentamethylene tetramine 5 Titanium dioxide 3 Paraffin wax 6 The wax was melted into one-quarter of the plasticizer and transferred to a paste mixer. Talc, glycerol monooleate, calcium stearate and titanium dioxide were added and blended to form a smooth paste. The resin and onehalf of the remaining plasticizer were added to produce a very viscous mass. Mixing was continued for 15 minutes to produce a substantially homogeneous paste. The remaining plasticizer was added with stirring to form a flowable paste. The batch was then discharged over an inclined plane to remove coarse air bubbles. During mixing the temperature was maintained between 3246 C.

The plastisol thus produced was applied to a number of metal crowns with a high speed automatic lining machine of the type well known in the industry where the crowns are spun on a revolving chuck beneath a pressure nozzle which expels a small quantity of compound onto each crown. The quantity applied was 0.330 gms. per crown, and the spin of the chuck spread the compound across the inner face of the crown. The crowns so lined were transferred to a 205 C. electric oven with circulating air currents and were heated for one minute. Upon removal from the oven, the crowns were cooled. The liners were tough and rubbery with hundreds of fine cells dispersed throughout.

The majority of the cells were non-communicating, while some formed sinuous passages with each other. The exposed surface was substantially impervious.

I claim:

1. A process of providing a crown cap with a compres sible, cellular liner comprising: forming a fluid plastisol composition containing as essential ingredients a vinyl resin, a plasticizer and a blowing agent having a decomposition temperature slightly below the final fluxing temperature of said plastisol composition, the amount of said plasticizer being in the range of 60% to 120% based on the weight of said vinyl resin and the amount of said blowing agent being in the range of 0.1% to 5.0% by weight based on the weight of said plastisol composition, applying said plastisol composition to the inner surface of a crown cap with a high speed lining machine wherein less than 0.40 gram of said plastisol composition is placed within said crown cap while said crown cap is spinning and thereby spread across the inner face of said crown cap, said spinning being the only method used to configure said cellular liner; heating said crown cap so lined to a temperature above about 177 C. to transform said plastisol composition into a viscous gel and decompose said blowing agent, and cooling said viscous gel to transform the same into a rubbery, resilient cellular liner having a substantially impervious structure.

2. A process of providing a crown cap with a compressible, cellular liner comprising: forming a fluid plastisol composition containing as essential ingredients a vinyl resin, a plasticizer and a blowing agent having a decomposition temperature about 15 to 30 C. below the final fiuxing temperature of said plastisol composition, the amount of said plasticizer being in the range of 65% and 95% based on the weight of said vinyl resin and the amount of said blowing agent being less than 1.5% by weight based on the weight of said plastisol composition;

applying said plastisol composition to the inner surface of a crown cap with a high speed lining machine wherein about 0.33 gram of said plastisol composition is placed within said crown cap while said crown cap is spinning and thereby spread across the inner face of said crown cap, said spinning being the only method used to configure said cellular liner; heating said crown cap so lined to a temperature of about 205 C. to transform said plastisol composition into a viscous gel, said blowing agent decomposing to produce a myriad of non-communicating gas cells of predominantly uniform size in said gel; and cooling said viscous gel to transform the same into a rubbery, resilient cellular liner having a substantially impervious surface.

References Cited in the file of this patent UNITED STATES PATENTS 2,256,483 Johnston Sept. 23, 1941 2,371,868 Berg et a1. Mar. 20, 1945. 2,387,730 Alderson Oct. 30, 1945 2,427,699 Aronovsky et al Sept. 23, 1947 2,489,407 Foye Nov. 29, 1949 2,654,913 Maier Oct. 13, 1953 2,663,909 Maier et a1. Dec; 29, 1953 2,684,774 Aichele July 27, 1954 2,744,042 Pace May 1, 1956 2,752,059 Schneider June 26, 1956 2,888,414 Fuller May 26, 1959 OTHER REFERENCES British Plastics, pp. 86-88. 

2. A PROCESS OF PROVIDING A CROWN CAP WITH A COMPRESSIBLE, CELLULAR LINER COMPRISING: FORMING A FLUID PLASTISOL COMPOSITION CONTAINING AS ESSENTIAL INGREDIENTS A VINYL RESIN, A PLASTICIZER AND A BLOWING AGENT HAVING A DECOMPOSITION TEMPERATURE ABOUT 15* TO 30*C. BELOW THE FINAL FLUXING TEMPERATURE OF SAID PLASTISOL COMPOSITION, THE AMOUNT OF SAID PLASTICIZER BEING IN THE RANGE OF 65% AND 95% BASED ON THE WEIGHT OF SAID VINYL RESIN AND THE AMOUNT OF SAID BLOWING AGENT BEING LESS THAN 1.5% BY WEIGHT BASED ON THE WEIGHT OF SAID PLASTISOL COMPOSITION; APPLYING SAID PLASTISOL COMPOSITION TO THE INNER SURFACE 